CPU_UCODE not working in a custom kernel

I've got a custom kernel with most everything stripped out. It built
fine yesterday, but today, after adding "options CPU_UCODE" it fails to
build.

It appears that the file firmload.c is not being included in the build,
probably because my stripped down kernel does not include any of the
devices that would drag in firmload.c (a quick check shows that the list
of drivers would be ral and bwi).